function popImage(title, image) {

    var viewportwidth;
    var viewportheight;
    
    var winwidth = 640;
    var winheight = 420;
      
    // the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
    if (typeof window.innerWidth != 'undefined') {
      viewportwidth = window.innerWidth;
      viewportheight = window.innerHeight;
    // IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
    } else if (typeof document.documentElement != 'undefined' && typeof document.documentElement.clientWidth != 'undefined' && document.documentElement.clientWidth != 0) {
       viewportwidth = document.documentElement.clientWidth;
       viewportheight = document.documentElement.clientHeight;
    // older versions of IE  
    } else {
       viewportwidth = document.getElementsByTagName('body')[0].clientWidth;
       viewportheight = document.getElementsByTagName('body')[0].clientHeight;
    }
    
    var winx = Math.round((viewportwidth - winwidth)/2);
    var winy = Math.round((viewportheight - winheight)/2);
 
    window.open('/catalog/includes/image_pop.php?ttl='+title+'&img='+image,"Image","menubar=no,width="+winwidth+",height="+winheight+",left="+winx+"px,top="+winy+"px,toolbar=0,location=0,scrollbars=1");
}